Author Topic: Davis sensors worth it?  (Read 718 times)

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Offline threesixright

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Davis sensors worth it?
« on: August 23, 2019, 03:48:56 AM »
Hi All!

New to the forum  8-) Please be gentle  :oops:

Software engineer by trade, almost hitting the magic five-zero  :roll: and living in the Czech Republic (being a expat) [tup]

We are going to move to country side, and some weather station is something on my mind. Trying to figure out what to get is easier said then done!

For some reason I'm ending up with Davis all the time, although I find their console outdated (looks like DOS form the old days). I can't ignore the very good reviews. I also can't ignore the hefty price tag  #-o So my question, the console aside, is the big difference the quality of the sensors (lets say compare to Froggit)?

My main interest are:
- Wind (speed & direction)
- Rain
- Temperature & humidity
- UV levels

I was also looking at the protocol of the sensor as the are being fed into the ISS, is this somewhere documented? So reading the raw signals without the ISS.

Thanks you all!

Offline johnd

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Re: Davis sensors worth it?
« Reply #1 on: August 23, 2019, 04:51:49 AM »
Not much help I'm afraid, but only you can make the decision about how much you're comfortable spending - ultimately it's subjective. To a first approximation, more money buys you a better station - more accuracy, more reliability, better support etc etc - but it's not linear, eg a Vaisala station is probably not 5-10x better than a Davis, despite that being (very roughly) the price differential. But high-end applications like airfields will nonetheless typically opt for Vaisala or a comparable high-end brand.

It's a clue that Davis is much more prepared to publish detailed specifications, including accuracy, than some of the cheaper competition (who else offers something comparable to https://www.davisinstruments.com/product_documents/weather/spec_sheets/6152_62_53_63_SS.pdf for instance) and these specs are backed by independent trials. You can obviously do a comparative review of the specs for yourself (not confusing reading resolution with accuracy). Don't overlook aspects like aftersales support, which may be close to nonexistent for some cheaper brands, other than perhaps user forums. I would argue that Davis or a similar brand like RainWise (but who have a much lower profile than Davis in Europe) is the cheapest 'serious' station you can buy, but I know that some won't agree.

Re data direct from the ISS: You need to specify whether it's a cabled or wireless unit you're thinking of - with wireless you obviously need a compatible wireless receiver. One resource for the message formats is at: https://github.com/dekay/DavisRFM69/wiki
« Last Edit: August 23, 2019, 06:39:59 AM by johnd »
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Offline chief-david

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Re: Davis sensors worth it?
« Reply #2 on: August 23, 2019, 08:20:44 AM »
I think my davis is dependable. and has an update rate of 2.5 seconds. Rarely do you miss data. 

The UV and Solar are cool. Although I do know when I need to have sunscreen on without looking at it.
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Offline PaulMy

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Re: Davis sensors worth it?
« Reply #3 on: August 23, 2019, 08:54:13 AM »
You can't go wrong with a Davis!

Enjoy,
Paul
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Offline ConligWX

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Re: Davis sensors worth it?
« Reply #4 on: August 23, 2019, 08:57:46 AM »
Also all new Davis vPro2 Weather Stations come with the new Rain gauge to improve accuracy.  I've own both a Vantage Vue and now a Davis Vantage Pro2 plus. both have performed very well and I dont think i'd go for anything else tbh.

Offline johnd

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Re: Davis sensors worth it?
« Reply #5 on: August 23, 2019, 09:22:52 AM »
Also all new Davis vPro2 Weather Stations come with the new Rain gauge to improve accuracy.

Please be careful not to raise false expectations. Only when existing stocks of VP2 stations and the spare/standalone rain gauges are exhausted at Davis (and then further down the supply chain too) will this be true. Some station versions will see the change sooner than others depending on the level of buffer stocks at Davis and elsewhere, but it may be into 2020 before some of the slower selling units all have the spoon.

FWIW (and IMHO of course) it's not clear if the spoon is more accurate, though I think what you can say about it is that it's easier to calibrate because it's just a single screw adjustment rather than trying to balance the effects of two screws.
« Last Edit: August 23, 2019, 09:26:48 AM by johnd »
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Offline threesixright

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Re: Davis sensors worth it?
« Reply #6 on: August 23, 2019, 09:34:45 AM »
Thank you all for the replies!

@johnd
I meant signals (data) as they are coming direct from the sensor. I have to assume that the sensors are the same wether your use cable or wireless? So I'm after the raw sensor data (and their protocol). 

This is a page where they explain the wind speed and direction for a Davis anemometer. I'm looking for slimmelar information for the other Davis sensors.
http://cactus.io/projects/weather/arduino-weather-station-davis-anemometer

I guess the rain bucket is nothing but a pulse when the spoon tips over?

Which leaves the temperature, humidity and uv sensor  :oops:

With regard to v2: Is there anyway how to see if the Davis comes with the newer version of the rainbucket?

Offline ConligWX

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Re: Davis sensors worth it?
« Reply #7 on: August 23, 2019, 11:02:40 AM »
If you purchase from a recommended reseller then they will should sell the vPro2 with a new rain sensor, subject to stock I guess. not sure if they upgrade any old units or they are sent back to Davis for upgrade. before purchasing you can always ask. 

As to the protocol i'm not that sure, you could ask Boris (Meteobridge) as his MB Pro reads Davis ISS RF data directly, which means you dont required a console, though most do use them.

I'm not sure however if someone has intercepted a Davis sensor without the ISS reading it first, and not sure why you would really want to do it any other way as you would require your own power for the sensors to work, would you not?
« Last Edit: August 23, 2019, 11:20:21 AM by ConligWX »

Offline johnd

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Re: Davis sensors worth it?
« Reply #8 on: August 23, 2019, 11:20:35 AM »
If you purchase from a recommended reseller then they will sell the vPro2 with a new rain sensor. not sure if they upgrade any old units or they are sent back to Davis for upgrade. before purchasing you can always ask. 

That's not actually how it works.
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Offline ConligWX

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Re: Davis sensors worth it?
« Reply #9 on: August 23, 2019, 11:30:54 AM »
it's not clear if the spoon is more accurate, though I think what you can say about it is that it's easier to calibrate because it's just a single screw adjustment rather than trying to balance the effects of two screws.

since fitting the upgraded rain gauge 7 days ago its definitely performing more accurate than my last tipping bucket and on par with 3 local Met Office stations. I also fitted a CocoRaHS Rain Gauge in the back garden to compare against the new Davis Rain Gauge. So far they are just about equal. time of course will tell however  [tup]

Offline Bushman

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Re: Davis sensors worth it?
« Reply #10 on: August 23, 2019, 12:25:47 PM »
....
Which leaves the temperature, humidity and uv sensor  :oops:

...

All the specs are on the Davis website.
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Offline johnd

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Re: Davis sensors worth it?
« Reply #11 on: August 24, 2019, 04:12:21 AM »
@johnd: I meant signals (data) as they are coming direct from the sensor.

Well the sensor inputs into the transmitter board are, all but one, analogue (assuming you might count simple contact closures from the wind speed sensor and rain gauge as analogue - in a sense they're analogue signals that need to be counted within a specified time window).

The only exception (other than pressure, which you didn't ask about) is the temp/hum sensor which is digital, but then if you were rolling your own sensor interface board I guess you'd prefer to use the I2C version of the SHT31 rather than its Sensibus version that Davis still uses (or choose a different T/H sensor altogether, albeit maybe still a Sensirion one). Details of the T/H messages will be found on the Sensirion website.
« Last Edit: August 24, 2019, 04:35:44 AM by johnd »
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